1. Field of the Invention
This invention pertains generally to a device for determining the height, direction, period and wavelength of the principal ocean wave component, and more particularly to making measurements on a moving surface or subsurface vehicle.
2. Description of the Related Art
The current methods for determining the height, direction, period and wavelength of the principal ocean wave component require the use of moored or bottom mounted instrumentation systems whose primary disadvantage is that they are costly and time consuming to deploy and recover, and are thus only suitable for making measurements in a single location. The moored systems cannot directly measure wavelength since wave height is only measured at a single point.
Bottom mounted systems use an array of pressure sensors that provide full spectrum measurement of wave height, direction, period and wavelength. These systems are only effective in shallow water where the pressure effects of the surface waves can be sensed on the bottom.
Small buoys, such as a wave rider, can be used in moderately deep water. These buoys are allowed to swing around their moorings and a heading sensor is used to determine wave direction.
Permanently moored large buoys, such as those used by NOAA, measure wave height and provide coarse measurement of wave direction.
The object of this invention is to provide a device for measuring the height, direction, period and wavelength of the principal ocean wave component on a moving surface or subsurface vehicle.
This and other objectives are achieved by the shipboard wave measurement system (SWMS) that makes measurements as a function of time of vehicle position, range from the vehicle to the water""s surface, and vehicle heave, pitch and roll to compute the height, direction, period and wavelength of the principal ocean wave component. Since the vehicle is moving, the wave heights measured are at different spatial locations, as well as at different times, and the observed wave height signal is Doppler shifted. The SWMS is composed of a positioning device, a timing device, a wave height estimator (WHE), a Doppler Integrator (DI) and a computer. The positioning device measures the vehicle""s position, the timing device provides accurate time referencing for the vehicle position and wave height measurements. The wave height estimator measures range to the water""s surface from the vehicle and vehicle vertical acceleration, pitch and roll and generates wave height at specific instants of time. The Doppler integrator receives the referenced wave height signal from storage and generates the frequency and height of the principal wave component, both as a function of time.